EnviroNearby

Skagit County, Washington air quality history

Daily Air Quality Index summaries from EPA monitors in Skagit, Washington, 1996–2025.

98%
Good days in 2025
25
Median daily AQI, 2025
0
Days above 100 in 2025
363
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Skagit, Washington on 363 days. 354 of those days (98%) were in the Good range, and the median daily AQI was 25. That median is lower than the typical monitored county in Washington (median 28 across 30 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 304 days. Across the years with fuller monitoring, the share of Good days fell: an average of 100% in 1996–1998 versus 96% in 2023–2025.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1996: Good 248 of 249 days1996: Moderate 1 of 249 days19961997: Good 323 of 323 days1998: Good 349 of 349 days1999: Good 350 of 352 days1999: Moderate 2 of 352 days2000: Good 332 of 353 days2000: Moderate 21 of 353 days2001: Good 347 of 358 days2001: Moderate 11 of 358 days20012002: Good 351 of 353 days2002: Moderate 2 of 353 days2003: Good 354 of 361 days2003: Moderate 7 of 361 days2004: Good 363 of 366 days2004: Moderate 3 of 366 days2005: Good 360 of 365 days2005: Moderate 5 of 365 days2006: Good 354 of 365 days2006: Moderate 11 of 365 days20062007: Good 320 of 365 days2007: Moderate 42 of 365 days2007: Unhealthy for Sensitive Groups 3 of 365 days2008: Good 330 of 366 days2008: Moderate 26 of 366 days2008: Unhealthy for Sensitive Groups 9 of 366 days2008: Unhealthy 1 of 366 days2009: Good 327 of 364 days2009: Moderate 37 of 364 days2010: Good 336 of 365 days2010: Moderate 21 of 365 days2010: Unhealthy for Sensitive Groups 3 of 365 days2010: Unhealthy 3 of 365 days2010: Very Unhealthy 2 of 365 days2011: Good 345 of 365 days2011: Moderate 20 of 365 days20112012: Good 357 of 366 days2012: Moderate 9 of 366 days2013: Good 280 of 365 days2013: Moderate 85 of 365 days2014: Good 319 of 365 days2014: Moderate 46 of 365 days2015: Good 284 of 365 days2015: Moderate 80 of 365 days2015: Unhealthy for Sensitive Groups 1 of 365 days2016: Good 331 of 366 days2016: Moderate 35 of 366 days20162017: Good 325 of 365 days2017: Moderate 40 of 365 days2018: Good 325 of 365 days2018: Moderate 32 of 365 days2018: Unhealthy for Sensitive Groups 5 of 365 days2018: Unhealthy 3 of 365 days2019: Good 340 of 365 days2019: Moderate 25 of 365 days2020: Good 266 of 272 days2020: Moderate 6 of 272 days2021: Good 296 of 314 days2021: Moderate 17 of 314 days2021: Unhealthy for Sensitive Groups 1 of 314 days20212022: Good 313 of 365 days2022: Moderate 47 of 365 days2022: Unhealthy for Sensitive Groups 4 of 365 days2022: Unhealthy 1 of 365 days2023: Good 336 of 365 days2023: Moderate 29 of 365 days2024: Good 357 of 366 days2024: Moderate 9 of 366 days2025: Good 354 of 363 days2025: Moderate 9 of 363 days2025
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001996: 90th percentile AQI 411997: 90th percentile AQI 301998: 90th percentile AQI 321999: 90th percentile AQI 362000: 90th percentile AQI 422001: 90th percentile AQI 402002: 90th percentile AQI 372003: 90th percentile AQI 442004: 90th percentile AQI 402005: 90th percentile AQI 412006: 90th percentile AQI 432007: 90th percentile AQI 522008: 90th percentile AQI 502009: 90th percentile AQI 512010: 90th percentile AQI 472011: 90th percentile AQI 432012: 90th percentile AQI 422013: 90th percentile AQI 552014: 90th percentile AQI 522015: 90th percentile AQI 552016: 90th percentile AQI 502017: 90th percentile AQI 512018: 90th percentile AQI 522019: 90th percentile AQI 462020: 90th percentile AQI 392021: 90th percentile AQI 462022: 90th percentile AQI 522023: 90th percentile AQI 482024: 90th percentile AQI 412025: 90th percentile AQI 401996: Median AQI 271997: Median AQI 191998: Median AQI 221999: Median AQI 252000: Median AQI 282001: Median AQI 272002: Median AQI 252003: Median AQI 312004: Median AQI 282005: Median AQI 282006: Median AQI 312007: Median AQI 342008: Median AQI 312009: Median AQI 282010: Median AQI 312011: Median AQI 292012: Median AQI 312013: Median AQI 392014: Median AQI 362015: Median AQI 392016: Median AQI 342017: Median AQI 352018: Median AQI 322019: Median AQI 292020: Median AQI 212021: Median AQI 282022: Median AQI 332023: Median AQI 302024: Median AQI 262025: Median AQI 251996200120062011201620212025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Fine particles (PM2.5)30484%
Ozone5916%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536335490000254057PM2.5
202436635790000264159PM2.5
2023365336290000304893PM2.5
20223653134741003352183PM2.5
20213142961710002846101PM2.5
202027226660000213957PM2.5
2019365340250000294659PM2.5
20183653253253003252190PM2.5
2017365325400000355199PM2.5
2016366331350000345080Ozone
20153652848010003955116PM2.5
2014365319460000365277PM2.5
2013365280850000395564PM2.5
201236635790000314271Ozone
2011365345200000294386PM2.5
20103653362133203147205Ozone
2009364327370000285161PM2.5
20083663302691003150153PM2.5
20073653204230003452143Ozone
2006365354110000314367Ozone
200536536050000284161Ozone
200436636330000284058Ozone
200336135470000314477Ozone
200235335120000253758Ozone
2001358347110000274074Ozone
2000353332210000284275Ozone
199935235020000253662Ozone
199834934900000223245Ozone
199732332300000193038Ozone
199624924810000274161Ozone

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Washington with a similar median AQI in 2025

All monitored counties in Washington

Source: U.S. EPA AirData, “Annual AQI by County” files for 1996–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem